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MAINE DEPARTMENT OF ENVIRONMENTAL PROTECTION www.maine.gov/dep

The ability of streams to withstand the

effects of urbanization Tom Danielson, PhD

Leon Tsomides Doug Suitor

MAINE DEPARTMENT OF ENVIRONMENTAL PROTECTION

Protecting Maine’s Air, Land and Water


Overview

• Lessons learned from Impervious Cover study

• Factors that make streams more resilient or vulnerable to urbanization


Impervious Surfaces


Stream Watersheds




Spatial Resolution Matters

• We computed % IC with 3 spatial layers. – 30m resolution

• 2001 National Land Cover Data (NLCD) – 5m resolution

• 2004 Maine Land Cover Data (MELCD) – 1m resolution

• 2004 MELCD and MEIFW


Advancements in IC Estimates


Advancements in IC Estimates


2001 NLCD – 30m resolution

30m


2004 MELCD – 5m resolution

5m


2004 MELCD – 1m resolution

1m


Spatial Resolution Matters

• 5 m spatial compared to 1 m spatial data – overestimates % IC in urban and suburban

areas – underestimates % IC in rural areas


Impervious Cover Thresholds

Previous studies have found threshold effects on stream biota ranging from 1-15% IC.


Stream Classes

% OF LINEAR MILES OF STATUTORY CLASSIFICATIONS

Class AA = 6%

Class A = 45%

Class B = 47%

Class C = 2%


Biomonitoring Results %

Impe

rvio

us C

over

0

10

20

30

40

50

AA/A B C NA

A

Macroinvertebrate Result

0

10

20

30

40

50

AA/A B C NA

B

Algae Result

~25% of data

~25% of data

~25% of data

~25% of data

median

Tom Danielson, Maine DEP


Risk of Not Attaining Biological Criteria

% Impervious Cover

0 5 10 15 20

High Risk

High Risk

High Risk

Low Risk

Low Risk

Class AA/A

Class B

Class C


IC Targets

• “How much IC is too much for this watershed?”

• “What is a good restoration target for this watershed?”

• Answer: “Well, it depends.”


Factors that Influence Resilience of Streams to

Urbanization


1. Condition of Riparian Zone

Kennedy Brook, Augusta

Penjajawoc Stream, Bangor

Whitten Brook, Skowhegan


Riparian Zones • Sites with more IC in

50 m buffer zone had less Mayfly, Stonefly, and Caddisfly (EPT) Taxa

• The size of points indicates the amount of IC in a 50m buffer zone

0 10 20 30 40 50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

% IC

EP

T re

lativ

e ric

hnes

sEP

T Ta

xa R

elat

ive

Ric

hn

ess

Watershed % IC


2. Condition of Headwaters

Perkins Brook, Waterville


3. Stream Channel Alteration

Unnamed Stream, Waterville Lindsay Brook, Rockland


4. Habitat Fragmentation


5. Road Crossings and Culverts

Concord Gully, Freeport, Source: MPBN Tributary to Bond Brook, Augusta


6. Water Source


7. Watershed Connection

Fall Brook, Portland


8. Agriculture

Fence Protects Stream Cows in Stream


source: NRCS

source: NWF

Buffer Strips and Contour Tilling

Erosion from Traditional Tilling


9. Groundwater Quality

Fish Brook, Fairfield

Upstream Control Downstream Impact


10. Nutrient Enrichment

Capisic Brook, Portland


11. Salt Application

Source: Road Salt Institute


Salt Pile


Salt Pile

2,750 µS/cm

1,600 µS/cm


12. Polluted Runoff

Birch Stream, Bangor


Take Home Messages • There are different ways to measure IC • There is more to urbanization than IC • A variety of factors make streams more or

less resilient to urbanization • Urbanization can impact aquatic life at

very low levels


www.maine.gov/dep [email protected]

http://www.maine.gov/dep